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# AC BASIC AND NETWORKS

## Characteristics Impedance :-

It is defined as ratio of positively traveling voltage wave to current wave at any point online. It is also known as natural impedance.
Characteristics Impedance,

√ R + j2πfL
Z0   =   -------------------- ohms
√  G + j2πfC

Propagation constant of line,

Gamma (γ)= ( α ) Alpha + j(β) beta

Here α is real of propagation constant and it's measure of changes in magnitude Of current or Voltage in each section and is called attenuation constant. And β is an
Imaginary part of propagation and is the difference in phase angle between the input Current and the output Current or the corresponding voltage and is called phase shift constant.

Gamma(γ) =√ ZY = √ ( R + j2πfL ) ( G + j2πfC)

Phase velocity of propagation,

2π
Vp = λ f   = --------
β ( beta)
2π
And wavelength  λ=  -------
β
Characteristics impedance is fixed by the geometry of two conductors. For a parallel wire line with insulation, it is

276               d
Calculated as Z0  =  ---------- log e ----
√k                 r

Where  d = Distance between conductor
Centres
k = Relative permittivity of
Insulation between Conductors
For a coaxial transmission line, The characteristics Impedance is calculated as

138              d1
Z0 = --------- log e ------
√k                d2

Where d1 = Inside diameter of outer
Conductor
d2 = Outside diameter of inner
Conductor

Velocity factor of cable,

Velocity of wave propagation
=  ----------------------------------------------
Velocity of light in vacuum

v         1
= ----- = ------
c       √k